This invention relates generally to clothes washing machines, and more particularly to clothes washing machines of the top loading type having a resiliently mounted, non-rotary outer tub and an internal spin tub rotating about a vertical axis.
Clothes washing machines of the top loading type have a cabinet comprising a base, four sidewall portions, and a top having therein a lid to allow access into the spin tub, which usually has an agitator mounted on the axis and which, in turn, is rotatably mounted within an outer tub. Generally, the spin basket is perforate to allow water removal during centrifugal extraction, while the outer tub is imperforate and serves to contain the liquid washing medium. The outer tub has a mounting assembly which includes a transmission, drive motor, and pump, and is resiliently mounted to absorb vibration from unbalanced loads that occur particularly during the acceleration and high speed during the spin or centrifuging portion of the cycle. While many arrangements are provided for mounting the tub, transmission, and other components, a common arrangement is to have them mounted on a dome-type assembly on the base and anchored by springs extending between the tub mounting assembly and the base to hold the entire outer tub and related assemblies in a centered position with regard to the sidewalls of the cabinet and the top opening. Generally, the outer tub is made as small as possible to provide a minimum clearance around the spin tub, so as to minimize the amount of water used in a wash cycle. Of course, it is possible to select various fill levels for water during the portions of the cycle.
Of particular concern with machines of this type is the necessity for avoiding excessive movement of the outer tub and mounting assembly because of unbalanced loads of clothes in the spin tub during the spin operation, and particularly during the acceleration phase of the spin tub when, depending upon the amount and location of the load, it is possible to encounter resonant frequencies which could result in excessive excursions of movement, causing the outer tub to strike the walls of the cabinet. While such excessive excursions can be prevented by using an unbalance switch which detects such excessive movements of the tub and de-energizes the drive motor, so that the clothes can be physically rearranged to correct the unbalance, it is desirable to tolerate certain excursions during the spin-up portion of the cycle, since such excursions in the movement of the tub may substantially decrease once the full spin speed is reached.
In order to minimize the magnitude of the excursions of the tub, it is possible to increase the force of the centering springs, but if these are made too stiff, other problems may be encountered as a result of the complex dynamics of the rotating system. However, generally two other approaches are used, both of which involve increasing the mass of the suspended tub assembly so as to thereby decrease the effects of unbalanced loads. One such approach is simply to increase the weight of the outer tub assembly, preferably at a point as high above the base as possible. This can be done by adding weights to the exterior of the tub, as disclosed in U.S. Pat. No. 3,475,928. Another approach has been to use a weight ring at the top of the spin basket, as shown in T. R. Smith U.S. Pat. No. 2,926,136, which has an additional gyroscopic stabilizing effect during spin because of the rotation of the mass.
While the first of these solutions has the advantages of being relatively simple and low cost in manufacture, it does require substantially heavier weights than the rotating ring, and these weights add to shipping costs and make the unit more difficult to move if necessary for service. Furthermore, such weights function only when attached to the outer tub, and when such tub is made of a heavy steel construction, no problem is presented. However, if the outer tub is made of a plastic material, to decrease the weight and increase the corrosion resistance of the unit, such material is not stiff enough to support the weights in their normal position.
On the other hand, while a rotating annular ring of weighted material at the top of the spin tub does not require nearly the mass of the stationary weights, it does require a much more complex and precise construction for the spin tub to avoid any unbalance caused by nonuniformity of the balance ring itself. Heretofore, such balance rings have usually been built into the spin tub structure itself, using several walls and an inwardly projecting structure which is difficult to form with a high degree of accuracy, since such tubs are usually made of a porcelain enameled steel, which is easily distorted under the high temperatures required for the porcelain enameling operation. For this reason, the use of a heavy weight ring built into the top of the spin tub has resulted in an increased cost of manufacture over the external weight arrangement.
Another problem presented by such top loading washing machines is the necessity to control the clothes within the spin tub and prevent their escape therefrom. For example, if small articles of clothing come out of the spin tub and enter the space between the spin tub and the outer tub, it is almost impossible to remove them without disassembling the machine, and they can reach locations where they can cause substantial damage upon continued operation of the machine. For this reaason, it is a usual construction to provide a clothes guard in the form of an annular piece that mounts at the top on the inside of the spin tub and extends toward the central axis so that small clothing articles are retained within the spin tub.
Likewise, to ensure that space between the spin tub and the outer tube is not readily accessible, an annular cover is used over the outer tub extending radially inward over the clothes guard on the spin tub, and generally provides a configuration to define an opening which corresponds with the opening through the top of the cabinet to prevent the possibility that during the filling or removal of clothes any such clothes can pass outwardly above the outer tub and fall down into the mechanism within the cabinet. Such tub cover generally also functions to mount such items as bleach dispensers and lint filters, and generally provides the mount for the fill nozzle by which the tub is filled during the wash and rinse cycles. The fill nozzle mounted in the tub cover generally is intended to spray downwardly on the clothes which may be adhering to the sides of the spin tub, as is particularly desirable in the case of a spray rinse after the first centrifugal extraction cycle of the washing medium, but since the machine is generally not rotating during other fill cycles, this results in a concentration of the incoming water at a particular spot. To overcome this, it has been proposed that the fill system use a tube extending around the bottom side of the tub cover inwardly of any projection of the spin tub or clothes guard and having openings to spray downwardly on the clothes. Such an arrangement is shown in U.S. Pat. No. 3,663,975, in which a rubber tube is mounted on the underside and has a plurality of slots so that the spray water is distributed over the entire periphery of the spin basket and the clothes therein, even when the basket is not rotating during a fill operation. However, such a construction has required the use of a rubber tube for mounting purposes, and the openings in such tube can easily be distorted with wear and age, and have little control over the radial direction of spray during a fill or rinse cycle.